Method and device for optical recording onto optical disc medium

ABSTRACT

There is provided an optical recording method for directing a recording pulse train to an optical disc medium to form marks thereon and for recording information as information about the edge positions of said marks and the spaces between marks, the recording pulse train having been created by modulating laser light into plural power levels. The method includes: coding to-be-recorded data into coded data consisting of the combination of marks and spaces; classifying said marks within said coded data on the basis of the mark length and the preceding or succeeding space lengths of the marks; shifting the position of the second pulse edge counted from the end portion of the recording pulse train for forming said marks, depending on the result of said classification, to adjust said recording pulse train; and directing said recording pulse train to the optical disc medium to form said marks thereon.

This application is a Divisional Application of Ser. No. 10/583,320,which is the National Stage of International Application No.PCT/JP2005/000065 filed Jan. 6, 2005.

TECHNICAL FIELD

The present invention relates to optical recording methods and opticalrecording apparatuses for recording information onto an optical discmedium by directing laser light thereto to form marks thereon.

BACKGROUND ART

Optical discs such as DVD-RAMS are phase-change discs includingamorphous marks which have been formed on the recording film bydirecting laser light thereto and controlling the laser power duringheating for changing the cooling ratio of the recording film. In orderto increase the information transfer rate during recording andreproducing onto and from these optical disc mediums, the recordinglinear density may be increased or the scanning speed of a light spotover the recording medium can be increased. In order to increase therecording linear density, mark lengths and space lengths themselves maybe reduced or mark lengths and space lengths may be varied minutely toreduce the time intervals of detection of mark edge positions. However,the method of increasing the recording linear density will cause theproblem of the S/N ratio of reproducing signals, thus making itimpossible to largely increase the recording linear density.

In the case of reducing the lengths of to-be-recorded marks and spacesin order to increase the recording density, particularly if the spacelengths are made small, this will cause heat interferences, that is,heat of the ending end portion of a recorded mark may be transferredthrough the space region to affect the temperature rise at the startingend portion of the next mark or heat of the starting end portion of arecorded mark may affect the cooling process at the ending end portionof the previously-formed mark. Prior-art recording methods have had theproblem that the occurrence of heat interferences causes fluctuations ofmark edge positions thereby increasing the error ratio duringreproduction.

Furthermore, even when marks and spaces are formed on a disc to haveaccurate lengths, there may be caused the problem that the detected edgepositions of short marks and spaces are deviated from ideal valuesduring reproduction, due to the frequency characteristics of thereproducing optical system which depend on the size of the light spot.Such deviations of detected edges from the ideal values are generallyreferred to as inter-code interferences. There has been the problem thatwhen the sizes of marks and spaces are smaller than the light spot,significant inter-code interferences are caused to increase jitterduring reproduction, thus increasing the error ratio.

Therefore, there have been disclosed methods which drive laser powerwith binary values and change the positions of the starting end portionsof marks depending on the mark lengths and the preceding space lengthsof to-be-recorded marks while changing the positions of the ending endportions of marks depending on the mark lengths and the succeeding spacelengths of to-be-recorded marks, as shown in Japanese Patent PublicationNo. 2679596. Thus, the methods compensate the occurrences of heatinterferences between marks during high-density recording and inter-codeinterferences due to the frequency characteristics during reproduction.

Further, there have been disclosed methods which drive laser power withthree or more values and change the positions of the starting endportions of marks depending on the mark lengths of to-be-recorded markswhile changing the positions of the ending end portions of marksdepending on the mark lengths of to-be-recorded marks during recording,as shown in Japanese Patent Laid-open Publication No. 2004-185796. Thus,the methods compensate the occurrences of heat interferences betweenmarks during high-density recording and inter-code interferences due tothe frequency characteristics during reproduction There is alsodisclosed a method of adjusting the ending end positions of marks bychanging the widths of cooling pulses, in such cases.

FIGS. 13A to 13D and 13F are views illustrating examples of marks andspaces in a recording code row and the recording waveform generatingoperation for recording them, in a prior-art apparatus.

FIG. 13A represents reference-time signals 128 having a period of Tw,which serve as a time reference for the recording operation. FIG. 13Brepresents a recording code row 126 resulted from the NRZI conversion ofto-be-recorded data by the coder 113. Here, the Tw is also a detectingwindow width and is a standard unit of mark lengths and space lengths inthe recording code row 126. FIG. 13C represents an image of marks andspaces to be actually recorded on the optical disc and the laser lightspot is scanned in a direction from left to right in FIG. 13C. Marks 301correspond to the “1” level of the recording code row 126 with aone-to-one ratio and are formed to have lengths corresponding to thedurations thereof. FIG. 13D represents count signals 205 for measuringthe time elapsed since the heads of the marks 301 and the spaces 302 byusing the Tw as a unit.

FIG. 13F is an example of recording waveforms in a prior-art apparatuscorresponding to the recording code row of FIG. 13B. The recordingwaveforms 303 are created by referring to the count signals 205 and therecording code row 126.

FIGS. 14A to 14F are views illustrating examples of marks and spaces ina recording code row and the recording waveform generating operation forrecording them, in a prior-art apparatus. FIG. 14A representsreference-time signals 128 having a period of Tw, which serve as a timereference for the recording operation. FIG. 14B represents a recordingcode row 126 resulted from the NRZI conversion of to-be-recorded data bythe coder 113. Here, the Tw is also a detecting window width and is astandard unit of mark lengths and space lengths in the recording coderow 126. FIGS. 14C to 14F are timing charts illustrating the waveformsof recording pulse signals 125 during the formation of recording markshaving mark lengths of 2 T to 5 T. The recording pulse signals 125 havebeen subjected to level modulation to have three levels which are ahighest-level peak power (Pw), a medium-level erasing power (Pe) and alowest-level bottom power (Pb) in the case of FIG. 14C.

With the prior-art recording compensation, the amount of shift dT_(top)by which the starting position of each head pulse is shifted from thereference-time signals is changed depending on the mark length of theto-be-recorded mark as described above, to change the starting endposition of the recorded mark. Further, the amount of shift dTe by whichthe ending position of the cooling pulse is shifted from thereference-time signals is changed depending on the mark length of theto-be-recorded mark to change the ending end position of the recordedmark.

With the aforementioned first prior-art technique, the power ismodulated with binary values. Therefore, in the case of performingmulti-pulse recording onto a medium such as a phase-change type discwhich enables controlling the formation of marks with the cooling rateof heated portions, the next light pulses are directed thereto beforethe heated portions are sufficiently cooled, which prevents normal markformation. Namely, there has been the problem that marks are formed tobe teardrop shapes and thus normal marks cannot be formed due toexcessive amounts of heat injection.

Further, when minute marks have been formed during the mark formingprocess, marks having minimum mark lengths cause significant inter-codeinterferences. To cope with this, in order to correct the frequencycharacteristics of the reproducing optical system, an electricalfrequency correcting circuit (equalizer) may be used to reduce theinter-code interferences. However, the boost value of the equalizer isincreased especially during the formation of minute marks. When theinter-code interferences in the reproducing system are eliminated byincreasing the boost value of the equalizer, noise components inhigh-frequency regions are increased, thus making it impossible toprovide preferable jitter.

Further, with the aforementioned second prior-art technique, the endingend positions of cooling pulses are adjusted during compensation of markending edges for facilitating recrystallization of the ending endportions of the mark to adjust the positions of ending end portions ofthe to-be-recorded mark.

However, in the case of a rerecordable-type optical recording mediumemploying an inorganic material, the formation of marks haveirreversible characteristics and thus includes no recrystallizationprocess of the recording film, which makes it impossible to adjust markending end positions by adjusting the widths of cooling pulses, in somemediums. In the case of such mediums, jitter at the mark ending endpositions will be increased, thus causing increases of the error ratioof reproducing signals.

As described above, the aforementioned prior-art techniques cannotenable the formation of marks with sufficient accuracy duringhigh-density recording and consequently cannot realize sufficientrecording surface densities and sufficient reliability.

Therefore, it is an object of the present invention to provide opticalrecording methods and optical recording apparatuses which are capable ofrecording onto various types of optical disc mediums while accuratelycompensating heat interferences and inter-code interferences.

SUMMARY OF THE INVENTION

An optical recording method according to the present invention is anoptical recording method for directing a recording pulse train to anoptical disc medium to form marks thereon and for recording informationas information about the edge positions of the aforementioned marks andthe spaces between marks, the recording pulse train having been createdby modulating laser light into plural power levels, wherein the methodincludes:

coding to-be-recorded data into coded data consisting of the combinationof marks and spaces;

classifying the aforementioned marks within the aforementioned codeddata on the basis of the mark length and the preceding or succeedingspace lengths of the marks;

shifting the position of the second pulse edge counted from the endportion of the recording pulse train for forming the aforementionedmarks, depending on the result of the aforementioned classification, toadjust the aforementioned recording pulse train; and

directing the aforementioned recording pulse train to the optical discmedium to form the aforementioned marks thereon.

An optical recording apparatus according to the present invention is anoptical recording apparatus for directing a recording pulse train to anoptical disc medium to form marks thereon and for recording informationas information about the edge positions of the aforementioned marks andthe spaces between marks, the recording pulse train having been createdby modulating laser light into plural power levels, wherein theapparatus includes:

coding unit operable to code to-be-recorded data into coded dataconsisting of the combination of marks and spaces;

classifying unit operable to classify the aforementioned marks withinthe aforementioned coded data on the basis of the combination of themark length and the preceding or succeeding space lengths;

recording wave generator operable to create a recording pulse train forcreating the aforementioned marks in which the position of the secondpulse edge counted from the end portion thereof has been shifteddepending on the result of the aforementioned classification; and

laser driving unit operable to direct the aforementioned recording pulsetrain to the optical disc medium to form the aforementioned marksthereon.

As described above, with the optical recording method according to thepresent invention, marks to be recorded are classified by mark lengthand preceding or succeeding space lengths and the position of the secondpulse edge counted from the end portion of a recording pulse train forrecording each mark is shifted by an amount of edge shift dT_(F2) and/ordT_(E2) depending on the result of the aforementioned classification toadjust the recording pulse signals. This enables accurately controllingthe starting end position and the ending end position of the mark to beformed on the optical disc medium. Further, the pulse edge is adjusteddepending on the preceding or succeeding space lengths as well as on themark length of the to-be-recorded mark, thus controlling the startingend position and the ending end position of the mark more accurately inconsideration of inter-code interferences. This can improve thereliability of the recording/reproducing operation and realizeminiaturization of the information recording apparatus and the recordingmedium at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become readily understood from the followingdescription of preferred embodiments thereof made with reference to theaccompanying drawings, in which like parts are designated by likereference numeral and in which:

FIG. 1 is a block diagram illustrating the structure of an opticalrecording apparatus according to a first embodiment of the presentinvention;

FIGS. 2A to 2F are timing charts in the optical recording methodaccording to the first embodiment of the present invention;

FIGS. 3A to 3F are timing charts illustrating the relationship betweenthe mark lengths and the recording waveforms of recording pulse trains,in the optical recording method according to the first embodiment of thepresent invention;

FIGS. 4A to 4D are views illustrating an example of the control ofrecording pulse trains in the optical recording method according to thefirst embodiment of the present invention;

FIGS. 5A to 5D are views illustrating another example of the control ofrecording pulse trains in the optical recording method according to thefirst embodiment of the present invention;

FIGS. 6A to 6D are views illustrating a further example of the controlof recording pulse trains in the optical recording method according tothe first embodiment of the present invention;

FIG. 7 is a flow chart in the optical recording method according to thefirst embodiment of the present invention;

FIG. 8 is a flow chart of a method for creating a recording compensatingtable, in the optical recording method according to the first embodimentof the present invention;

FIGS. 9A to 9F are timing charts illustrating the relationship betweenthe mark lengths and the waveforms of recording pulse trains, in theoptical recording method according to a second embodiment of the presentinvention;

FIGS. 10A to 10J are timing charts illustrating the relationship betweenthe mark lengths and the waveforms of recording pulse trains, in theoptical recording method according to a third embodiment of the presentinvention;

FIGS. 11A to 11D are schematic views illustrating the waveforms ofreproducing signals in a reproducing method according to a fourthembodiment of the present invention;

FIG. 12 is a view illustrating the waveform equalizing characteristicsin the reproducing method according to a fourth embodiment of thepresent invention;

FIGS. 13A to 13D and 13F are timing charts in a prior-art opticalrecording method; and

FIGS. 14A to 14F are timing charts illustrating the relationship betweenthe mark lengths and the recording waveforms of recording pulse trains,in a prior-art optical recording method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described.While in these embodiments phase-change optical discs will beexemplified as recording media, the present invention is not limitedthereto and is techniques common to recording mediums which enablerecording information therein by injecting energy thereto to form markshaving physical characteristics different from those of non-recordedportion.

First Embodiment

FIG. 1 is a block diagram illustrating the structure of an opticalrecording/reproducing apparatus according to the first embodiment of thepresent invention. This optical recording/reproducing apparatusincludes, as a recording system, a coder 113, a reference-time generator119, a counter 200, a classifier 201, a recording waveform generator112, a recording compensator 118, a laser driving circuit 111, a powersetting device 114, a laser 100 and an optical system including anobjective lens 116. Further, this optical recording/reproducing deviceincludes, as a reproducing system, the optical system including adetecting lens 106, a light detector 100, a preamplifier 101, a waveformequalizer 103, a binarizer 104, a decoder 105, and a reproducing-shiftdetermining device 170. Further, the aforementioned optical systemincludes a collimating lens 109 and a half mirror 108, in addition tothe objective lens 116 and the detecting lens 106.

First, the respective components of the optical recording/reproducingdevice will be described.

The coder 113 converts to-be-recorded data 127 into a recording code row(NRZI) 126 which is information about the mark lengths, the spacelengths and the positions of the heads of marks and spaces to be formedon an optical disc 117. The recording code row 126 is transferred to theclassifier 201, the recording waveform generator 112 and the counter200.

The classifier 201 classifies the marks within the recording code row126, by mark length (code length) and preceding or succeeding spacelengths, in accordance with a predetermined rule. The classifier 201inputs the result, as classification signals 204, to the recordingwaveform generator 112.

The counter 200 refers to the recording code row 126, measures the timeelapsed since the positions of the heads of marks using reference-timesignals 128 generated from the reference-time generator 119 as the unitand creates count signals 205. The coder 113 and the recording waveformgenerator 112 are operated in synchronization with the reference-timesignals 128. The reference-time signals 128 are created by readingsignals from wobbles on the disc 117 and applying a PLL thereto forestablishing synchronization thereof.

The recording compensator 118 reads information pre-recorded on acertain region of the disc, holds recording compensating table data andoutputs the recording compensating table data to the recording waveformgenerator, wherein the recording compensating table data defines theamounts of pulse-position shifts by which the recording pulse waveformsare to be shifted by the recording waveform generator in accordance withthe mark lengths and the preceding or succeeding space lengths.

The recording waveform generator 112 compensates, along a time axis,pulse-shaped waveforms in accordance with NRZI rows, classificationsignals and the recording compensating table data. Thus, the NRZI rowsare converted into recording pulse signals 125 corresponding torecording waveforms. Recording pulse signals 125 are formed by threelevels depending on the laser power level.

The recording compensator 118 stores a recording compensating tabledefining the amounts of edge shifts dT_(F2) and/or dT_(E2) by which theposition of the second pulse edge counted from the end portion of therecording pulse signal 125 is shifted, as will be described later. Therecording compensator 118 sends the recording compensating table to therecording waveform generator 112 and causes it to send, to the laserdriving circuit, recording pulse signals 125 including recording pulses,wherein the positions and the widths of the respective recording pulseshave been compensated by classifying the pulses for respective marklengths on the basis of the classification signals.

The laser driving circuit 111 sets the laser powers corresponding to thethree levels (Pw, Pe, Pb) of recording pulse signals 125 to the powerlevels set by the power setting device 114 and drives the laser 110 witha laser driving current 124 for directing pulse-shaped light to theoptical disc 117 to create recording marks thereon.

Next, there will be described a method for recording information onto anoptical disc 117 with the recording system of the opticalrecording/reproducing apparatus.

Recording pulse signals 125 are sent to the laser driving circuit 111.The laser driving circuit 111 refers to the recording pulse signals 125and the powers set by the power setting device 114 and generates laserdriving currents 124 according to the levels of the recording pulsesignals 125 for causing the laser 110 to generate light in accordancewith predetermined recording waveforms of the recording pulse signals125. The laser light 123 generated from the laser 110 is focused ontothe optical disc 117 through the collimating lens 109, the half mirror108 and the objective lens 116 and heats the recording film to formmarks and spaces.

Next, there will be described a reproducing method executed in thereproducing system of the optical recording/reproducing apparatus.

During reproduction of information, laser light 123 at a low power levelwhich will not corrupt recorded marks is scanned over the mark row onthe optical disc 117. The reflected light from the optical disc 117 ispassed through the objective lens 116 and the half mirror 108 and isdirected to the detecting lens 106. The laser light is passed throughthe detecting lens 106 and is focused onto the light detector 100. Thefocused light is converted into electric signals depending on thestrength of the light-intensity distribution on the light detector 100.The preamplifier 101 provided on the light detector 100 amplifies theelectrical signals into reproducing signals 120 in accordance with thepresence and absence of marks at the scanned position on the opticaldisc 117. The waveform equalizer 103 applies a waveform equalizingprocess to the reproducing signals 120 and the binarizer 104 changesthem to binary data consisting of “0” or “1” and then applies a PLL tothe data for establishing synchronization thereof to convert it intobinarized reproducing signals 121. The decoder 105 applies conversioninverse to that of the coder 113 to the binarized reproducing signals121 to create reproducing data 122.

The reference-time signals have a frequency of 66 MHz and a Tw of about15 nsec, for example. The disc is rotated at a constant linear speed of4.92 m/sec. As the laser light, a semiconductor laser with a wavelengthof 405 nm is employed. The objective lens has an NA of 0.85. The opticaldisc 117 may be a single-layer disc including a single layer which has arecording surface capable of recording information thereon or adouble-layer disc including two layers provided at one side, each layerhaving a recording surface capable of recording information thereon.Also, the optical disc medium 117 may be either a rewritable-typeoptical disc medium employing a phase-change recording material or awrite-once type optical disc medium capable of recording only a singletime. The manner of coding may be 17PP modulation or 8-16 modulation, aswell as (1,7) modulation. In the case of (1,7) modulation and 17PPmodulation, the smallest code length will be 2 Tw. In the case of 8-16modulation, the smallest code length will be 3 Tw, which may be treatedas a code length provided by the present embodiment employing (1,7)modulation plus one.

FIGS. 2A to 2F are views illustrating examples of marks and spaces in arecording code row and the recording waveform generating operation forrecording them, in the optical recording/reproducing apparatus.

FIG. 2A represents reference-time signals 128 having a period of Tw,which serve as a time reference for the recording operation. FIG. 2Brepresents a recording code row 126 resulted from the NRZI conversion ofto-be-recorded data by the coder 113. Here, the Tw is a detecting windowwidth and is a minimum unit of the amount of the changes of mark lengthsand space lengths in the recording code row 126. FIG. 2C represents animage of marks and spaces to be actually recorded on the optical discand the laser light spot is scanned in a direction from left to right inFIG. 2C. Marks 301 correspond to the “1” level of the recording code row126 with a one-to-one ratio and are formed to have lengths correspondingto the durations thereof. FIG. 2D represents count signals 205 formeasuring the time elapsed since the heads of the marks 301 and thespaces 302 by using the Tw as a unit.

FIG. 2E is a schematic view of the classification signals 204 in therecording/reproducing apparatus, wherein the marks are classified by thecombination of three values which are the mark length and the precedingor succeeding space lengths of each mark, in the present embodiment. Forexample, in FIG. 2E, “4-5-2” represents a mark having a mark length of 5Tw, a preceding space length of 4 Tw and a succeeding mark length of 2Tw. Also, in some cases, w may be omitted and the respective lengths maybe represented as 4 T and 2 T. Also, in some cases, the space lengthsmay be represented as 4 Ts while the mark length is represented as 2 Tm.

FIG. 2F represents recording pulse signals corresponding to therecording code row 126 of FIG. 2B, as an example of light waveforms tobe actually recorded. These recording pulse signals 125 are created byreferring to the count signals 205, the recording code row 126, theclassification signals 204 and the recording compensating table dataoutput from the recording compensator 118.

Then, there will be described a recording compensating method in theoptical recording/reproducing apparatus.

FIGS. 3A to 3F are schematic views illustrating the relationship betweenthe mark lengths of marks and the recording waveforms of the recordingpulse signals 125. FIG. 3A represents reference-time signals 128 havinga period of Tw, which serve as a time reference for the recordingoperation. FIG. 3B represents count signals 205 generated from thecounter 200 for measuring the time elapsed since the mark heads usingthe reference time Tw of the reference-time signals 128 as the unit. Thetiming of the transition of the count signal to 0 corresponds to theheads of marks or spaces. FIGS. 3C to 3F are recording pulse signals 125during the formation of recording marks. The recording pulse signals 125have been subjected to level modulation to have three levels which are ahighest-level peak power (Pw), a medium-level erasing power (Pe) and alowest-level bottom power (Pb). Further, after the last pulse, a coolingpulse is formed at the bottom power level.

Although the recording pulse signals 125 have been subjected tomodulation to have three power level values, recording pulse signals maybe subjected to modulation to have a total of four power levels suchthat the bottom power level of the cooling pulse after the last pulse isdifferent from the bottom power level between middle pulses. Although,in FIGS. 3A to 3F, the bottom power level is a power level lower thanthe erasing power level, the bottom power level may be an intermediatepower level between the erasing power level and peak power level.Although in FIGS. 3C to 3F the recording pulse signal for a 4 Tw-markincludes a single middle pulse, the number of middle pulses increasesone by one as the mark length (code length) increases 1 Tw by 1 Tw to 5Tw or 6 Tw.

According to this recording compensation (adaptive compensation), marksare classified by mark length and preceding or succeeding spaces, andthe position of the second-pulse edge counted from the end portion ofthe recording pulse train for recording the respective marks by anamount of edge shift dT_(F2) or/and dT_(E2) according to theaforementioned result of classification to control the recording pulsesignal, thus accurately controlling the starting end position and theending end position of the marks to be formed on the optical discmedium. When the positions of the starting end portions dT_(top) and theending end portions dTe of recording pulse trains are shifted as in theprior art, the starting end positions and the ending end positions ofmarks are largely shifted, thus preventing accurate control. By shiftingthe position of the second-pulse edge counted from the end portion ofthe recording pulse signal by an amount of edge shift dT_(F2) or/anddT_(E2) as previously described, the starting end position and theending end position of the mark can be controlled more accurately.Further, the pulse edges are controlled depending on the preceding orsucceeding space lengths as well as on the mark lengths of marks to berecorded, thus controlling the starting end positions and the ending endpositions of the marks more accurately in consideration of interferencebetween codes.

There will be described a recording compensating method used for theoptical recording method, using a flow chart of FIG. 7.

(a) First, to-be-recorded data is coded to create coded data consistingof a combination of marks and spaces (S01). This coded data correspondsto the recording code row 126 in FIG. 2B.

(b) The marks are classified by combinations of the mark length and thepreceding or succeeding space lengths (S02). In FIG. 2E, a 2 T-mark isrepresented as “2-2-3”, a 3 T-mark is represented as “3-3-4”, a 5 T-markis represented as “4-5-2”, and a 6 T-mark is represented as “2-6-2”.They are represented as a combination of “the preceding space length”,“the mark length” and “the succeeding space length”, which are arrangedin this order.

(c) The position of the second pulse edge counted from the end portionof the recording pulse train for forming marks is shifted depending onthe result of classification to adjust the recording pulse train (S03).For example, in FIG. 3C, the position of the second pulse edge countedfrom the starting end portion is shifted by an amount of edge shiftdT_(F2). In FIG. 3D, the position of the second pulse edge counted fromthe starting end portion is shifted by an amount of edge shift dT_(F2)and/or the position of the second pulse edge counted from the ending endportion is shifted by an amount of edge shift dT_(E2).

(d) The recording pulse train is directed to the optical disc medium 117to form marks (S04).

FIGS. 4A to 4D are schematic views illustrating a case of shifting theposition of the second pulse edge of a recording pulse train which iscounted from the starting end portion thereof by an amount of edge shiftdT_(F2), when recording a mark 301 having a mark length of 4 T. FIG. 4Ais reference-time signals 128 which serve as a time reference for therecording operation and FIG. 4B is count signals 205 generated from thecounter 200. FIG. 4C is a recording pulse train 125 in which theposition of the second pulse edge counted from the starting end portionhas been shifted by an amount of edge shift dT_(F2). FIG. 4D is a viewillustrating an image of a mark 301 having a mark length of 4 T recordedby the recording pulse train of FIG. 4C, wherein there is shown that thestarting end position thereof can be accurately controlled. The amountof edge shift dT_(F2) is defined on the basis of the result ofclassification by mark length and preceding space length of theto-be-recorded mark, as represented in the following Table. 1.

TABLE 1 The mark length dT_(F2) 2T 3T >=4T The preceding 2T a1 a2 a3space length 3T a4 a5 a6 4T a7 a8 a9 >=5T a10 a11 a12

As the amount of edge shift dT_(F2), a total of 3*4=12 types of values(a1 to a12) are defined for the mark lengths of to-be-recorded markswhich are classified into three types of mark lengths 2 T, 3 T and 4 Tand more and for the preceding space lengths classified into four typesof spacing lengths 2 T, 3 T, 4 T and 5 T and more. While in this casethe amounts of edge shifts dT_(F2) are classified into a total of 12types for three types of mark lengths and four types of preceding spacelengths, the present invention is not limited thereto. For example, atotal of 16 types of amounts of edge shifts may be defined for fourtypes of mark lengths similarly. Also, the mark lengths may beclassified into two, five or more types of mark lengths and thepreceding space lengths may be classified into two, three, five or moretypes of preceding space lengths. Also, the amount of edge shift dT_(F2)may be defined as absolute time values such as a1=5 nsec or integralmultiples of Tw/16 on the basis of the reference-time signals.

As described above, by shifting the position of the second pulse edge ofthe recording pulse signal which is counted from the starting endportion by an amount of edge shift dT_(F2), the starting end position ofthe mark can be adjusted more accurately. Further, the pulse edge isadjusted depending on the preceding space length as well as on the marklength of the mark to be recorded, thus adjusting the starting endposition of the mark 301 more accurately in consideration of inter-codeinterference.

FIGS. 5A to 5D are schematic views illustrating a case of shifting theposition of the second pulse edge of a recording pulse train which iscounted from the ending end portion thereof by an amount of edge shiftdT_(E2), when recording a mark 301 having a mark length of 4 T. FIG. 5Aand FIG. 5B are similar to FIG. 4A and FIG. 4B. FIG. 5C is a recordingpulse train 125 in which the position of the second pulse edge countedfrom the ending end portion thereof has been shifted by an amount ofedge shift dT_(E2). FIG. 5D is a view illustrating an image of a mark301 having a mark length 4 T recorded by the recording pulse train ofFIG. 5C, wherein there is shown that the position of the ending endportion thereof can be accurately adjusted. The amount of edge shiftdT_(E2) is defined on the basis of the result of classification by marklength and succeeding space length of the to-be-recorded mark, asrepresented in the following Table. 2.

TABLE 2 The mark length dT_(E2) 2T 3T >=4T The succeeding 2T b1 b2 b3space length 3T b4 b5 b6 4T b7 b8 b9 >=5T b10 b11 b12

As the amount of edge shift dT_(E2), a total of 3*4=12 types of values(b1 to b12) are defined for the mark lengths of to-be-recorded markswhich are classified into three types of mark lengths 2 T, 3 T and 4 Tand more and for the succeeding space lengths classified into four typesof spacing lengths 2 T, 3 T, 4 T and 5 T and more. While in this casethe amounts of edge shifts dT_(E2) are classified into a total of 12types for three types of mark lengths and four types of succeeding spacelengths, the present invention is not limited thereto. For example, atotal of 16 types of amounts of edge shifts may be defined for fourtypes of mark lengths similarly. Also, the mark lengths may beclassified into two, five or more types of mark lengths and thesucceeding space lengths may be classified into two, three, five or moretypes of succeeding space lengths. Also, the amount of edge shiftdT_(E2) may be defined as absolute time values such as b4=6 nsec orintegral multiples of Tw/16 on the basis of the reference-time signals.

As described above, by shifting the position of the second pulse edge ofthe recording pulse signal which is counted from the ending end portionby an amount of edge shift dT_(E2), the ending end position of the markcan be adjusted more accurately. Further, the pulse edge is adjusteddepending on the succeeding space length as well as on the mark lengthof the mark to be recorded, thus adjusting the position of the endingend portion of the mark 301 more accurately in consideration ofinter-code interference.

In the recording pulse for a 2 T mark, dT_(F2) and dT_(E2) arecoincident at the same pulse edge position as in FIGS. 3A to 3F. Therewill be described a method for setting the amount of edge shift in thecase where two amounts of pulse edge shift are applied to the same pulseedge position as described above. For example, in the case of thearrangement of “3-2-4” for a 2 T mark having a preceding space length of3 T and a succeeding space length of 4 T in FIG. 2E, “a4” in Table. 1and “b7” in Table. 2 are selected. In this case, “a4+b7” is defined asdT_(F2) and dT_(E2) for the 2 T mark. By combining as described above,the pulse edge position can be shifted depending on the combination ofthe preceding space and the succeeding space when two amounts of edgeshift are applied to a single pulse edge.

FIGS. 6A to 6D are schematic views illustrating a case of shifting theposition of another pulse edge, in addition to shifting the position ofthe second pulse edge of the recording pulse train which is counted fromthe starting end portion thereof by an amount of edge shift dT_(F2)(FIG. 4C) and shifting the position of the second pulse edge countedfrom the ending end portion thereof by an amount of edge shift dT_(E2)(FIG. 5C). FIG. 6A and FIG. 6B are similar to FIG. 4A and FIG. 4B. FIG.6C is a recording pulse train 125, wherein there are collectivelyrepresented a case of shifting the position of the second pulse edgecounted from the starting end portion by an amount of edge shiftdT_(F2), a case of shifting the position of the second pulse edgecounted from the ending end portion by an amount of edge shift dT_(E2),a case of shifting the position of the pulse edge at the starting endportion by an amount of edge shift dT_(F1), a case of shifting theposition of the pulse edge at the ending end portion by an amount ofedge shift dT_(E1), a case of shifting the position of the third pulseedge counted from the starting end portion by an amount of edge shiftdT_(F3), and a case of shifting the position of the third pulse edgecounted from the ending end portion by an amount of edge shift dT_(F3).FIG. 6D is a view illustrating an image of a mark 301 having a marklength 4 T recorded by the recording pulse train of FIG. 6C, whereinthere is illustrated that the positions of the starting end portion andthe ending end portion can be accurately adjusted. The aforementionedamount of edge shift dT_(F1) is defined on the basis of the result ofclassification of to-be-recorded marks by mark length and precedingspace length, as represented in the following Table. 3. Theaforementioned amount of edge shift dT_(E1) is defined on the basis ofthe result of classification of to-be-recorded marks by mark length andsucceeding space length, as represented in the following Table. 4. Theaforementioned amount of edge shift dT_(F3) is defined on the basis ofthe result of classification of to-be-recorded marks by mark length andpreceding space length, as represented in the following Table. 5. Theaforementioned amount of edge shift dT_(E3) is defined on the basis ofthe result of classification of to-be-recorded marks by mark length andsucceeding space length, as represented in the following Table. 6.

TABLE 3 The mark length dT_(F1) 2T 3T >=4T The preceding 2T c1 c2 c3space length 3T c4 c5 c6 4T c7 c8 c9 >=5T c10 c11 c12

As the amount of edge shift dT_(F1), a total of 3*4=12 types of values(c1 to c12) are defined for the mark lengths of to-be-recorded markswhich are classified into three types of mark lengths 2 T, 3 T and 4 Tand more and for the preceding space lengths classified into four typesof spacing lengths 2 T, 3 T, 4 T and 5 T and more. While in this casethe amounts of edge shifts dT_(H) are classified into a total of 12types for three types of mark lengths and four types of preceding spacelengths, the present invention is not limited thereto. For example, atotal of 16 types of amounts of edge shifts may be defined for fourtypes of mark lengths similarly. Also, the mark lengths may beclassified into two, five or more types of mark lengths and thepreceding space lengths may be classified into one, two, three, five ormore types of preceding space lengths. Also, the amount of edge shiftdT_(F1) may be defined as absolute time values such as c6=5 nsec orintegral multiples of Tw/16 on the basis of the reference-time signals.

As described above, by shifting the position of the second pulse edge ofthe recording pulse signal which is counted from the end portion by anamount of edge shift dT_(F2) and/or dT_(E2) and further shifting theposition of the pulse edge at the starting end portion by an amount ofedge shift dT_(F1), it is possible to adjust the position of thestarting end portion of the mark 301 more accurately while adjusting itin somewhat larger units.

TABLE 4 The mark length dT_(E1) 2T 3T >=4T The succeeding 2T d1 d2 d3space length 3T d4 d5 d6 4T d7 d8 d9 >=5T d10 d11 d12

As the amount of edge shift dT_(E1), a total of 3*4=12 types of values(d1 to d12) are defined for the mark lengths of to-be-recorded markswhich are classified into three types of mark lengths 2 T, 3 T and 4 Tand more and for the succeeding space lengths classified into four typesof spacing lengths 2 T, 3 T, 4 T and 5 T and more. While in this casethe amounts of edge shifts dT_(E1) are classified into a total of 12types for three types of mark lengths and four types of succeeding spacelengths, the present invention is not limited thereto. For example, atotal of 16 types of amounts of edge shifts may be defined for fourtypes of mark lengths similarly. Also, the mark lengths may beclassified into two, five or more types of mark lengths and thesucceeding space lengths may be classified into one, two, three, five ormore types of succeeding space lengths. Also, the amount of edge shiftdT_(E1) may be defined as absolute time values such as d5=6 nsec orintegral multiples of Tw/16 on the basis of the reference-time signals.

As described above, by shifting the position of the second pulse edge ofthe recording pulse signal which is counted from the end portion by anamount of edge shift dT_(F2) and/or dT_(E2) and further shifting theposition of the pulse edge at the ending end portion by an amount ofedge shift dT_(E1), it is possible to adjust the position of the endingend portion of the mark 301 more accurately while adjusting it insomewhat larger units.

TABLE 5 The mark length dT_(F3) 3T >=4T The preceding 2T e1 e2 spacelength 3T e3 e4 4T e5 e6 >=5T e7 e8

As the amount of edge shift dT_(F3), a total of 2*4=8 types of values(e1 to e8) are defined for the mark lengths of to-be-recorded markswhich are classified into two types of mark lengths 3 T and 4 T and moreand for the preceding space lengths classified into four types ofspacing lengths 2 T, 3 T, 4 T and 5 T and more. While in this case theamounts of edge shifts dT_(F3) are classified into a total of 8 typesfor two types of mark lengths and four types of preceding space lengths,the present invention is not limited thereto. For example, a total of 12types of amounts of edge shifts may be defined for three types of marklengths 3 T, 4 T and 5 T and more similarly. Also, the mark lengths maybe classified into four, five or more types of mark lengths and thepreceding space lengths may be classified into one, two, three, five ormore types of preceding space lengths. Also, a constant amount of edgeshift may be employed. Also, the amount of edge shift dT_(F3) may bedefined as absolute time values such as e8=6 nsec or integral multiplesof Tw/16 on the basis of the reference-time signals.

TABLE 6 The mark length dT_(E3) 3T >=4T The succeeding 2T f1 f2 spacelength 3T f3 f4 4T f5 f6 >=5T f7 f8

As the amount of edge shift dT_(E3), a total of 2*4=8 types of values(f1 to f8) are defined for the mark lengths of to-be-recorded markswhich are classified into two types of mark lengths 3 T and 4 T and moreand for the succeeding space lengths classified into four types ofspacing lengths 2 T, 3 T, 4 T and 5 T and more. While in this case theamounts of edge shifts dT_(E3) are classified into a total of 8 typesfor two types of mark lengths and four types of succeeding spacelengths, the present invention is not limited thereto. For example, atotal of 12 types of amounts of edge shifts may be defined for threetypes of mark lengths 3 T, 4 T and 5 T and more similarly. Also, themark lengths may be classified into four, five or more types of marklengths and the succeeding space lengths may be classified into one,two, three, five or more types of succeeding space lengths. Also, aconstant amount of edge shift may be employed. Also, the amount of edgeshift dT_(E3) may be defined as absolute time values such as f6=5 nsecor integral multiples of Tw/16 on the basis of the reference-timesignals.

Also, the aforementioned amount of edge shift may be simply defined fortwo types of preceding or succeeding space lengths 2 T and 3 T and more,as in Tables. 7 to 10. In the case of performing high-density recordingby directing diaphragmed light to an optical disc, minimum recordedmarks and spaces are as small as the light spot, and therefore thesignals for shortest marks and shortest spaces may cause inter-codeinterferences, thus preventing recording or reproduction onto or fromaccurate edge positions due to the influence of the optical MTF.Therefore, when it is possible to provide sufficient recordingcharacteristics in consideration of inter-code interferences only byclassifying the space lengths into 2 T which is the minimum value andthe other space lengths, the amounts of edge shifts can be simplyclassified as previously described to offer the advantage of simplifyingthe recording compensating table, thereby simplifying the apparatus.

TABLE 7 The mark length dT_(F2) 2T 3T 4T >=5T The preceding 2T g1 g2 g3g4 space length >=3T g5 g6 g7 g8

TABLE 8 The mark length dT_(E2) 2T 3T 4T >=5T The succeeding spacelength 2T h1 h2 h3 h4 >=3T h5 h6 h7 h8

TABLE 9 The mark length dT_(F1) 2T 3T 4T >=5T The preceding 2T i1 i2 i3i4 space length >=3T i5 i6 i7 i8

TABLE 10 The mark length dT_(E1) 2T 3T 4T >=5T The succeeding spacelength 2T j1 j2 j3 j4 >=3T j5 j6 j7 j8

Also, as in Tables. 11 to 14, the amount of edge shift may be simplydefined such that the amounts of edge shift for the mark length 2 T andthe space length 2 T are different from the amounts of edge shifts formark lengths of 3 T or more and space lengths of 3 T or more. This isadvantageous when particularly small inter-code interferences occur inthe case of 3 Ts or more (spaces of 3 T or more) and 3 Tm or more (marksof 3 T or more).

TABLE 11 The mark length dT_(F2) 2T 3T >=4T The preceding space length2T k1 k2 k3 3T k4 k5 k6 4T k7 >=5T k8

TABLE 12 The mark length dT_(E2) 2T 3T >=4T The succeeding space length2T l1 l2 l3 3T l4 l5 l6 4T l7 >=5T l8

TABLE 13 The mark length dT_(F1) 2T 3T >=4T The preceding space length2T m1 m2 m3 3T m4 m5 m6 4T m7 >=5T m8

TABLE 14 The mark length dT_(E1) 2T 3T >=4T The succeeding space length2T n1 n2 n3 3T n4 n5 n6 4T n7 >=5T n8

Further, the recording compensating table designating the aforementionedrespective amounts of edge shift will be described.

The recording compensating table stored in the recording compensator 118may be either a recording compensating table provided by readinginformation which has been pre-recorded on an area of the optical disc117 which is called a read-in area during the fabrication of the disc orthereafter or a recording compensating table created from the result oflearning by actually performing test recording using predeterminedrecording pulse signals onto a test-writing region on the optical disc117, reproducing the test-written marks and the spaces and measuring theamounts of edge shifts for determining the condition which can offer themost preferable signal quality.

In the first method, the recording compensating table recording in apredetermined region of the optical disc 117 is obtained as reproducingdata and stored in the recording compensator 118.

Next, using a flow chart of FIG. 8, there will be described a method forcreating a recording compensating table by performing test-writing of apredetermined recording code row onto the optical disc 117, according tothe second method.

(a) Marks are classified by the combination of the mark length and thepreceding or succeeding space lengths, and the classified marks aretest-written (S11).

(b) The test-written marks and spaces are reproduced to generatereproducing signals (S12).

(c) On the basis of the reproducing signals, a table defining theamounts of pulse edge shifts in association with the combinations of themark lengths and the preceding or succeeding space lengths of the marksis created (S13). The reproducing signals are amplified by thepreamplifier 101 to be reproducing signals 120 and then passed throughthe waveform equalizer 103 and the binarizer 104 to be binarizedreproducing signals 121. The resultant binarized reproducing signals 121are also sent to the reproducing-shift determining device 170. Thereproducing-shift determining device 170 makes a comparison between thebinarized signals which has been synchronized through a PLL and thebinarized signals prior to the synchronization to determine the amountsof shifts for the respective marks and spaces and sends the result ofdetermination to the recording compensator 118.

Further, when test writing is executed using a test-writing region ofthe optical disc 117 as described above, recording may be repeatedlyperformed in order to update the recording compensating table data asrequired on the basis of the determined amount of edge shift, thenperform the aforementioned recording operation again and search arecording compensating table which can reduce the PLL clock and the edgeshifts in the binarized reproducing signals during reproduction.

Second Embodiment

FIG. 9 is a timing chart illustrating the relationship between the marklengths of marks to be recorded and the recording pulse signals 125, inan optical recording method according to the second embodiment of thepresent invention. This optical recording method is different from theoptical recording method according to the first embodiment in that thewidth Tlp of the last pulse at the peak power level (Pw) is adjusted inaccordance with the result of classification of marks by mark length andsucceeding space length. As the width of the last pulse Tlp, a total of2*4=8 types of values (o1 to o8) are defined for the mark lengths ofto-be-recorded marks which are classified into two types of mark lengths3 T and 4 T and more and for the preceding space lengths classified intofour types of spacing lengths 2 T, 3 T, 4 T and 5 T and more, asrepresented in the following Table. 15.

TABLE 15 The mark length Tlp 3T >=4T The preceding space length 2T o1 o23T o3 o4 4T o5 o6 >=5T o7 o8

By classifying the Tlp for respective succeeding space lengths insteadof classifying the dT_(E1) for respective succeeding space lengths asdescribed above, it is possible to accurately adjust the positions ofthe ending end portions of marks, particularly in the case ofrerecordable type recording mediums.

Third Embodiment

FIGS. 10A to 10J are timing chart illustrating the relationship betweenthe mark lengths of marks to be recorded and the recording pulse signals125, in an optical recording method according to the third embodiment ofthe present invention. This optical recording method is different fromthe optical recording method according to the first embodiment in thatthe recording pulse signals 125 have waveforms in which the number ofmiddle pulses is not proportional to the mark length value. According tothe optical recording method, as illustrated in FIGS. 10C to 10J, therecording pulse signals for marks having mark lengths of 2 Tw, 3 Tw and4 Tw have a single pulse at the peak power level. The recording pulsesignals 125 for marks having mark lengths of 5 Tw and 6 Tw have twopulses at the peak power level. The recording pulse signals 125 formarks having mark lengths of 7 Tw and 8 Tw have three pulses at the peakpower level. The recording pulse signal 125 for a mark having a marklength of 9 Tw has four pulses at the peak power level.

Further, when recording can be performed onto a signal recording mediumat different recording rates, both recording pulse signals of FIGS. 3Ato 3F and recording pulse signals of FIG. 10 can be used by switchingtherebetween depending on the recording transfer rate. For example,recording pulse signals of FIGS. 3A to 3F may be used for recording atlow recording transfer rates while recording pulse signals of FIGS. 10Ato 10J may be used for recording at high recording transfer rates.

While the pulses at the peak power level have a width of about 1 Tw andthe pulses at the bottom power level have a width of about 1 Tw in therecording pulse signals of FIGS. 10A to 10J, it is desirable that thepulses for respective mark lengths have widths of 0.5 Tw or more afterthe aforementioned recording compensation. In this case, response speedof the laser hardly influences the recording pulse signals, thusrelaxing the recording condition.

According to the optical disc recording method according to the presentembodiment, with the aforementioned series of operations, the positionsand the widths of the first and last pulses included in recording pulsescan be changed as required, for the positions of the starting endportions and the ending end portions of the marks, depending on the marklengths and the preceding or succeeding space lengths of to-be-recordedmarks, to reduce inter-code interferences during reproduction, thusproviding preferable signal quality.

Fourth Embodiment

There will be described a reproducing method using the opticalrecording/reproducing apparatus according to the present invention. Thisreproducing method is characterized by a waveform equalization havingfrequency characteristics illustrated in FIG. 12.

In the reproducing method, marks recorded on the optical disc 117 areread with laser light, and reproducing signals 120 are created using thedetecting lens 106, the light detector 100 and the preamplifier 101. Thereproducing signals 120 are changed to signals having frequencycharacteristics which have been corrected by the waveform equalizer 103.Further, the signals are converted into binarized reproducing signals121 by the binarizer 104 and then subjected to inverse conversion by thedecoder 105 to create reproducing data 122.

There will be observed attenuations of optical outputs depending on thefrequency. That is, among 2 Tw signals, 3 Tw signals, 4 Tw signals and 8Tw signals, etc., signals having higher frequencies such as 2 Tw signalswill have smaller reproducing amplitudes since such signals are createdfrom smaller marks. Thus, in order to correct such output attenuations,the characteristics of the equalizer is set such that signals havinghigher frequencies will have greater output amplitudes, in thereproducing method.

FIG. 12 is a view schematically illustrating the frequencycharacteristics of the waveform equalizer 103 (equalizer), wherein thereis represented the amplitude ratio of the output signal to the inputsignal. In the figure, the horizontal axis represents the signalfrequency and schematically represents the frequencies of a 2 Tw signal,a 3 Tw signal, a 4 Tw signal and a 8 Tw signal. The vertical axislogarithmically represents the output amplitude of the waveformequalizer 103. The waveform equalizer 103 may be a high-pass filter, aband-pass filter having a peak at a frequency which is slightly greaterthan the frequency corresponding to 2 Tw or the combination of them andamplifiers.

Consequently, as for marks and spaces, the smaller the minimum marklength, the greater the difference between the output amplitude of asignal having a high frequency such as a 2 Tw signal and the outputamplitude of a signal having a lower frequency such as a 8 Tw signal,namely the inclination of the characteristic curve. This increases thedifference between the output amplitude for the frequency of a 4 Twsignal, for example, and the output amplitude for the frequency of a 8Tw signal.

Therefore, it is desirable to provide characteristics which can preventpeak shifts in the reproducing frequency characteristics and change thenoise frequency distribution to improve the SNR (signal-to-noise ratio)of reproducing signals, thus improve the error rate of reproducingsignals.

FIGS. 11A to 11D are schematic views illustrating the difference in thereproducing-signal characteristics due to mark shape differences. FIGS.11A and 11C are schematic views of mark shapes after the formation ofrecording marks by scanning a light in a direction from left to right.FIGS. 11B and 11D illustrate reproducing signals generated by readingthe aforementioned marks with light having an intensity which will noterase the recorded marks, after the formation of the respective markshapes.

FIG. 11A is a schematic view illustrating a representative mark shape ona rewritable type medium using phase changes. A 2 Tw mark 1001 which issmallest is formed to be a ginkgo-shaped mark. The mark is formed to bea ginkgo-shaped mark since the cooling pulse has recrystallized the markending end portion thereof thereafter. FIG. 11B illustrates reproducingsignals during reproduction of the mark of FIG. 11A. In the case where a2 Tw mark and a 2 Tw space are adjacent to each other as in the figure,the reproducing signal amplitude becomes smallest. In this case, 12 isthe minimum amplitude.

On the other hand, FIG. 11C is a schematic view illustrating anexemplary mark shapes formed on a rerecordable-type disc using phasechanges. In a rerecordable-type disc, marks are formed without causingrecrestalization with cooling pulses. Therefore, a 2 Tw mark 1003 may beformed to be a round shape narrower in the widthwise direction thanother long marks. When a 2 Tw mark is formed to have a size smaller inthe widthwise direction than the sizes of other marks, the minimumamplitude 12 of the reproducing signals of FIG. 11D will be smaller thanthe minimum amplitude in FIG. 11B since it is affected by MTF, whichincreases inter-code interferences in the 2 Tw mark, thus causing areproducing peak shift.

If the peak boost value (Bp) is increased in the reproducing frequencycharacteristics of the waveform equalizer illustrated in FIG. 12, theamplitudes of reproducing signals will be increased and concurrentlynoise will be increased. Particularly, if the boost becomes excessive,this will increase noise in frequency ranges higher than thesignal-frequency range, thus causing detrimental problem of degradationof the S/N of reproducing signals. Further, under excessive boostconditions, lower-frequency components (4 Tw to 8 Tw) out of signalcomponents will cause large inter-code interferences, thus degrading thereproducing characteristics. Thus, when recording marks such as 2 Twmarks are drawn to be particularly smaller than other marks, inter-codeinterferences of 2 T marks can be compensated with the recordingcompensation based on only mark lengths, but inter-code interferencesdue to spaces are left, thus degrading the characteristics ofreproducing signals. Therefore, as previously described in theaforementioned embodiments, the second pulse edge counted from the endportion of the recording pulse signal is shifted by an amount of edgeshift dT_(F2) or/and dT_(E2) depending on the mark length and thepreceding or succeeding space lengths and further the starting edge andthe ending edge of the recording pulse signal are compensated,particularly in consideration of 2 Tw spaces, during recording of marks,to reduce inter-code interferences which have been caused by 2 Tw spacesin particular, thus improving the characteristics of reproducing signalseven when the boost value is low.

Further, in the case of recording data onto an optical recording mediumsuch as a rerecordable-type recording medium which enables recordingmarks thereon as in FIG. 10, the target boost value for recordingcompensation depends on the compensation accuracy of the recordingcompensation. For example, in the case of recording compensation withcompensation accuracy of about Tw/16, it is desirable that the boostvalue is increased by about 1 dB to 2 dB during recording. Also,recording may be first performed without space compensation during testwriting and, only when the reproducing signal characteristics such asthe jitter and the error ratio cannot satisfy reference values, then therecording operation with space compensation may be performed.

Also, first test writing may be performed using a code row created byeliminating signals for a minimum mark length from recording signals,then a recording compensating table for code lengths whose mark lengthsare 3 T or more may be created, then second test writing may beperformed with a code row including 2 Tw signals, and then a recordingcompensating table for signals including 2 Tw signals may be created.When the reproducing signal amplitude is extremely small as in FIG. 11D,if the position of the recording mark of a 2 Tw signal is not correct,this may make it difficult to correctly position longer marks and spaceshaving lengths of 3 Tw or more. In the case of reproducing signals whichwill cause significant inter-code interferences as previously described,it is possible to record marks having code lengths of 3 Tw or more atfirst, then perform accurate recording compensation of the edgepositions of the marks and spaces having code lengths of 3 Tw or more,subsequently record signals including 2 Tw signals and then accuratelycompensate the recording positions of the 2 Tw marks and spaces toenable recording more accurately and efficiently, thus improving thereproducing signal quality.

Further, when recording signals for code lengths of 3 Tw or more aspreviously described, the boost value of the reproducing equalizer maybe reduced by 1 dB or 2 dB from that for recording normal recording coderows including 2 Tw signals during recording compensation. In this case,since no 2 Tw signal is included, the reproducing signal amplitude isrelatively large and inter-code interferences occur moderately.Therefore, it is possible to record signals involving little edgeshifts, by adjusting the edge positions of long marks with a boost valueslightly smaller than normal boost values.

Further, while the respective embodiments of the present invention havebeen described by exemplifying the case of modulating the recordingpower with three laser power levels, it goes without saying thatmodulation with four power levels may be performed such that the powerlevel of cooling pulses is different from the bottom power level betweenmiddle pulses to offer equivalent effects.

Further, the present invention may be implemented in the followingconfigurations represented as various embodiments. According to a firstconfiguration, an optical recording/reproducing method of the presentinvention is an optical recording method for directing laser light to anoptical disc medium at plural powers by switching thereamong to recordinformation as information about the edge positions of marks and spaceshaving plural lengths, wherein the laser power is modulated into pulseshapes having three or more values such that a first power is greaterthan a second power and the second power is greater than a third power,during the formation of recording marks, the marks within a recordingcode row are classified by referring to the mark lengths (code length)and the preceding or succeeding space lengths, in accordance with apredetermined rule, the width or the starting position of the head pulsewithin a segment having the first power in the modulated pulses and thewidth or the ending position of the last pulse within the segment havingthe first power in the modulated pulses are changed as requireddepending on the aforementioned classification of the code lengthsduring recording to change the positions of the starting end portionsand the positions of the ending end portions of the recording marksduring recording.

According to a second configuration, in the opticalrecording/reproducing method of the present invention, for the positionsof the ending end portions of the aforementioned recording marks, thewidth or the ending position of the last pulse within a segment havingthe first power after modulation into the aforementioned pulse shapesare changed as required depending on the mark lengths and the succeedingspace lengths of the to-be-recorded marks.

According to a third configuration, in the optical recording/reproducingmethod of the present invention, for the positions of the starting endportions of the aforementioned recording marks, the width or thestarting position of the first pulse having the first power aftermodulation into the aforementioned pulse shapes are changed as requireddepending on the mark lengths and the preceding space lengths of theto-be-recorded marks.

According to a fourth configuration, in the opticalrecording/reproducing method of the present invention, the mark lengthswithin the recording code row are classified into at least three typesof code lengths which are n, n+1, and n+2 and more (n: a positiveinteger) and the space lengths preceding or succeeding theaforementioned mark lengths within the recording code row are classifiedinto at least two types of code lengths which are n and n+1 and more.

According to a fifth configuration, in the optical recording/reproducingmethod of the present invention, the mark lengths within the recordingcode row are classified into at least three types of code lengths whichare n, n+1, and n+2 and more and the space lengths preceding orsucceeding the aforementioned mark lengths within the recording code roware classified into at least four types of code lengths which are n andn+1, n+2 and n+3 and more.

According to a sixth configuration, in the optical recording/reproducingmethod of the present invention, the mark lengths within the recordingcode row are classified into at least three types of code lengths whichare n, n+1 and n+2 and more and, for the mark length n within theaforementioned recording code row, the space lengths preceding orsucceeding the aforementioned mark length (n) within the recording coderow are classified into at least four code lengths which are n, n+1, n+2and n+3 and more while for the mark lengths n+1 and n+2 and more withinthe aforementioned recording code row, the space lengths preceding orsucceeding the aforementioned mark lengths (n+1 and n+2 and more) withinthe recording code row are classified into at least two types of codelengths which are n and n+1 and more.

According to a seventh configuration, in the opticalrecording/reproducing method of the present invention, first testwriting is performed by classifying the mark lengths within therecording code row into at least three types of code lengths which aren, n+1 and n+2 and more and second test writing is performed byclassifying the space lengths preceding or succeeding the aforementionedmark lengths within the recording code row into at least four types ofcode lengths which are n, n+1, n+2 and n+3 and more.

According to a eighth configuration, in the opticalrecording/reproducing method of the present invention, recording isperformed with a recording code row including a row of codes having codelengths of n+1 or more during the aforementioned first test writing andrecording is performed with a recording code row including a row ofcodes having code lengths of n or more during the aforementioned secondtest writing.

According to a ninth configuration, in the optical recording/reproducingmethod of the present invention, the boost value of the reproducingequalizer for reproduction after the aforementioned second test writingis varied from that for reproduction after the aforementioned first testwriting.

According to a tenth configuration, in the optical recording/reproducingmethod of the present invention, the boost value of the reproducingequalizer for reproduction after the aforementioned second test writingis incremented by about 1 dB from that for reproduction after theaforementioned first test writing.

According to a eleventh configuration, an optical recording/reproducingapparatus includes an optical recording apparatus for directing laserlight to an optical disc medium at plural powers by switching thereamongfor forming marks having physical characteristics different from thoseof non-recorded portions, wherein the optical recording apparatusincludes laser-driving unit operable to modulate the power of the laserlight, coding means for converting information into recording code row,classifying unit operable to classify the marks in accordance with apredetermined rule by referring to the mark lengths (code lengths) andthe preceding or succeeding space lengths within the aforementionedrecording code row, and recording waveform generator operable to changethe width or the starting position of the head pulse within a segmenthaving a first power within the modulated pulses and the width or theending position of the last pulse within the segment having the firstpower within the modulated pulses, wherein the starting end positionsand the ending end positions of to-be-recorded marks are changeddepending on the classification by the aforementioned classifying unitduring recording.

According to a twelfth configuration, the optical recording/reproducingapparatus of the present invention includes driving unit operable todrive the laser by changing the width or the ending position of the lastpulse within a segment having the first power after modulation into theaforementioned pulse shapes as required depending on the mark lengthsand the succeeding space lengths of the to-be-recorded marks, for thepositions of the ending end portions of the aforementioned recordingmarks.

According to a thirteenth configuration, the opticalrecording/reproducing apparatus of the present invention includesdriving unit operable to drive the laser by changing the width or thestarting position of the first pulse having the first power aftermodulation into the aforementioned pulse shapes as required depending onthe mark lengths and the preceding space lengths of the to-be-recordedmarks, for the positions of the starting end portions of theaforementioned recording marks.

According to a fourteenth configuration, in the opticalrecording/reproducing apparatus of the present invention, theaforementioned classifying unit classifies the mark lengths within therecording code row into at least three types of code lengths which aren, n+1, and n+2 and more (n: a positive integer) and classifies thespace lengths preceding or succeeding the aforementioned mark lengthswithin the recording code row into at least two types of code lengthswhich are n and n+1 or more.

According to a fifteenth configuration, in the opticalrecording/reproducing apparatus of the present invention, theaforementioned classifying unit classifies the mark lengths within therecording code row into at least three types of code lengths which aren, n+1, and n+2 or more and classifies the space lengths preceding orsucceeding the aforementioned mark lengths within the recording code rowinto at least four types of code lengths which are n and n+1, n+2 andn+3 and more.

According to a sixteenth configuration, in the opticalrecording/reproducing method of the present invention, theaforementioned classifying unit classifies the mark lengths within therecording code row into at least three types of code lengths which aren, n+1 and n+2 and more and classifies the space lengths preceding orsucceeding the aforementioned mark length (n) within the recording coderow into at least four code lengths which are n, n+1, n+2 and n+3 andmore for the code length n within the aforementioned recording code rowwhile classifying the space lengths preceding or succeeding theaforementioned mark lengths (n+1 and n+2 and more) within the recordingcode row into at least two types of code lengths which are n and n+1 andmore, for the mark lengths n+1 and n+2 and more within theaforementioned recording code row.

According to a seventeenth configuration, in the opticalrecording/reproducing apparatus of the present invention, first testwriting is performed by classifying the mark lengths within therecording code row into at least three types of code lengths which aren, n+1 and n+2 and more and second test writing is performed byclassifying the space lengths preceding or succeeding the aforementionedmark lengths within the recording code row into at least four types ofcode lengths which are n, n+1, n+2 and n+3 and more.

According to a eighteenth configuration, in the opticalrecording/reproducing apparatus of the present invention, recording isperformed with a recording code row including a row of codes having codelengths of n+1 and more during the aforementioned first test writing andrecording is performed with a recording code row including a row ofcodes having code lengths of n or more during the aforementioned secondtest writing.

According to a nineteenth configuration, in the opticalrecording/reproducing apparatus of the present invention, the boostvalue of the reproducing equalizer for reproduction after theaforementioned second test writing is varied from that for reproductionafter the aforementioned first test writing.

According to a twentieth configuration, in the opticalrecording/reproducing apparatus of the present invention, the boostvalue of the reproducing equalizer for reproduction after theaforementioned second test writing is incremented by about 1 dB fromthat for reproduction after the aforementioned first test writing.

The optical recording method and the optical recording apparatus of thepresent invention are applicable to industries of electrical appliancesincluding digital electrical household appliances and informationprocessing apparatuses.

1-31. (canceled)
 32. An optical recording method for directing arecording pulse train to an optical disc medium to form marks and spacesthereon and for recording information as information about edgepositions of the marks and the spaces between the marks, the recordingpulse train having been created by modulating laser light into pluralpower levels, the method comprising: coding to-be-recorded data intocoded data consisting of a combination of the marks and the spaces; whenthe mark to be formed has a minimum mark length, shifting a position ofthe second pulse edge counted from a starting edge of the recordingpulse train for forming the marks and the spaces, depending on theresult of the classifying the marks each having a minimum mark length onthe basis of the minimum mark length and a space length of a precedingspace and a succeeding space, to adjust the recording pulse train; anddirecting the recording pulse train to the optical disc medium to formthe marks and the spaces thereon.
 33. An optical disc medium including arecording region for recording data by a method for directing arecording pulse train to the optical disc medium to form marks andspaces thereon and for recording information as information about theedge positions of the marks and the spaces between the marks, therecording pulse train having been created by modulating laser light intoplural power levels, the method comprising: coding to-be-recorded datainto coded data consisting of a combination of the marks and the spaces;when the mark to be formed has a minimum mark length, shifting aposition of the second pulse edge counted from a starting edge of therecording pulse train for forming the marks and the spaces, depending onthe result of the classifying the marks each having a minimum marklength on the basis of the minimum mark length and a space length of apreceding space and a succeeding space, to adjust the recording pulsetrain; and directing the recording pulse train to the optical discmedium to form the marks and the spaces thereon.
 34. Playbacking methodfor playbacking the optical disc medium as claimed in claim 33, whereinthe method comprises: directing second laser light to the optical discmedium, the second laser light having a laser power that is less thanthe power of the laser light used at the time of forming the marks andthe spaces; and obtaining the information about the edge positions ofthe marks and the spaces between the marks by receiving the second laserlight reflected from the optical disc medium, to playback the datarecorded on the optical disc medium on the basis of the informationabout the edge positions of the marks and the spaces between the marks.